(Table 1) Mean sizes of Hydrobia ulvae juveniles in the littoral zone of the Chernaya Inlet (Kandalaksha Bay, White Sea) in July-September 1995

Based on observations and experiments carried out within the White Sea silty-sandy littoral zone in 1994-1997 data on biology of development and behavior of Hydrobia ulvae juveniles over water column and in sediments were obtained. Hydrobiid juveniles 0.125-0.150 mm in size appear in plankton during the second half of June and in two to three weeks they precipitate on sediments reaching 0.300-0.350 mm in size. Specific biological features of the White Sea hydrobiids are a short reproductive period and a short period of juvenile growth related to long under-ice time and decelerated warming of shallow waters. Distribution of juvenile individuals of H. ulvae is primarily determined by hydrodynamics and microtopography of the littoral zone. Redistribution of the juveniles permanently takes place, since all size groups of the juveniles are equally subjected to migration. During the first few weeks after settling mortality of juvenile mudsnails is 85%.

(Table 1) Elemental mean values of the upper Paleocene and lower Eocene in IODP Hole 302-M0004A

We reconstruct the latest Paleocene and early Eocene (~57-50 Ma) environmental trends in the Arctic Ocean and focus on the Paleocene-Eocene thermal maximum (PETM) (~55 Ma), using strata recovered from the Lomonosov Ridge by the Integrated Ocean Drilling Program Expedition 302. The Lomonosov Ridge was still partially subaerial during the latest Paleocene and earliest Eocene and gradually subsided during the early Eocene. Organic dinoflagellate cyst (dinocyst) assemblages point to brackish and productive surface waters throughout the latest Paleocene and early Eocene. Dinocyst assemblages are cosmopolitan during this time interval, suggesting warm conditions, which is corroborated by TEX86'-reconstructed temperatures of 15°-18°C. Inorganic geochemistry generally reflects reducing conditions within the sediment and euxinic conditions during the upper lower Eocene. Spectral analysis reveals that the cyclicity, recorded in X-ray fluorescence scanning Fe data from close to Eocene thermal maximum 2 (~53 Ma, presence confirmed by dinocyst stratigraphy), is related to precession. Within the lower part of the PETM, proxy records indicate enhanced weathering, runoff, anoxia, and productivity along with sea level rise. On the basis of total organic carbon content and variations in sediment accumulation rates, excess organic carbon burial in the Arctic Ocean appears to have contributed significantly to the sequestration of injected carbon during the PETM.